JP2017219085A - Manufacturing method of spline telescopic shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spline telescopic shaft which can smoothly slide for a long period of time while securing a telescopic stroke.SOLUTION: In a masking process, tooth grooves G which are formed in a region of a metal core material 60 in an axial direction at a circumference equidistant in a peripheral direction are partially covered with a plurality of masking members 70 which are arranged at the circumference equidistant. In a resin coating process, a resin layer 43A is formed by supplying a synthetic resin to a surface of a tooth part (male spline 62), and an inner face of a part of the tooth grooves covered with the masking members 70 is left as a circumference equidistant metal exposure part 44. In a membrane forming process, a manufacturing intermediate body 40A and a broach 80 are made to relatively slide in an axial direction by press-fitting in a state that the manufacturing intermediate body 40A in which the resin layer 43A is formed is aligned with the broach 80 via the metal exposure part 44, and the resin layer 43A is scraped, thus forming a resin membrane.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a method for manufacturing a spline telescopic shaft.

For example, an intermediate shaft of a steering device is required to have a function of absorbing axial displacement so that vibrations from the road surface are not transmitted to the steering wheel.
Further, a steering shaft to which a steering wheel is connected at one end is required to have a function of expanding and contracting in the axial direction for position adjustment. For this reason, a spline telescopic shaft is used as an intermediate shaft or a steering shaft.

With this type of spline telescopic shaft, it is necessary that the inner shaft and the outer shaft slide smoothly and that no backlash occurs. Therefore, a resin film is formed on one of the tooth surfaces of the outer tooth portion of the inner shaft and the inner tooth portion of the outer shaft.
Usually, for example, after forming a resin layer on the surface of a metal core shaft having an external tooth portion by a flow dipping method or the like, the manufacturing intermediate with the resin layer formed is inserted into a die to scrape off excess resin. Thus, a resin film is formed.

If the manufacturing intermediate and the die are not sufficiently aligned when inserted through the die, the film thickness of the resin coating becomes uneven depending on the circumferential position. In that case, the thin-film side wears out and disappears early in long-term use, and the metal background is exposed, so that the spline telescopic shaft cannot slide smoothly. For this reason, the steering feeling is deteriorated.
In order to accurately align the manufacturing intermediate and the die, if the manufacturing intermediate has a metal exposed part in the range of the axial length longer than the specified length, it can be aligned using the metal exposed part. It is.

  For example, in Patent Document 1, the spline shaft portion of the inner shaft includes a first shaft portion coated with a synthetic resin film, and a second shaft portion that is a metal shaft portion disposed on the tip side of the first shaft portion. It consists of. When using the 2nd axis part which is a metal axis part of patent documents 1 for centering, it is possible to improve the accuracy of centering.

International Publication No. WO2015 / 137036

  However, the second shaft portion, which is a metal shaft portion, has a smaller diameter than the first shaft portion covered with the synthetic resin film, and is not meshed with the inner tooth portion of the outer shaft. That is, since the shaft length of the second shaft portion is not included in the mesh length between the inner shaft and the outer shaft, the mesh length is shortened (decreased), which is disadvantageous for wear resistance. In addition, the expansion / contraction stroke is limited on the spline expansion / contraction shaft having a restriction on the total length.

  An object of the present invention is to provide a spline telescopic shaft capable of realizing smooth sliding over a long period while securing a telescopic stroke.

  The invention of claim 1 is any one of a metal core (60) having a metal outer tooth portion (62) in a ring shape and a metal cylinder (60P) having a metal inner tooth portion (62P) in a ring shape. In the predetermined axial region (L1; L2) of the manufacturing intermediate body made of one part, a part of the tooth spaces (G) arranged in the circumferential equidistant direction (Y1) are arranged in the circumferential equidistant direction. A masking step of covering each with a plurality of masking members (70; 70P; 70R; 70Q; 70S), and supplying a synthetic resin to the surface of the tooth portion to form a resin layer (43A; 53PA), and the plurality of masking members A resin coating step for leaving the inner surfaces of some of the circumferential tooth grooves covered with a plurality of exposed metal portions (44; 54P) arranged at equal intervals in the circumference, and for manufacturing the resin layer formed thereon Intermediate (40A; 50PA) is a plurality of exposed metal parts In the state where the core is aligned with the broach (80; 80P), the resin intermediate layer and the broach are slid relative to each other in the axial direction by press fitting to scrape the resin layer to form a resin coating (43 And 53P), a method for producing a spline telescopic shaft (5; 5P).

In addition, although the alphanumeric character in a parenthesis represents the corresponding component etc. in embodiment mentioned later, this does not mean that this invention should be limited to those embodiment as a matter of course. The same applies hereinafter.
As in claim 2, in the masking step, a connecting member (71; 71P; 71S) that connects one end (70a; 70Pa; 70Sa) of the plurality of masking members (70; 70P; 70S) is formed in the manufacturing process. You may contact | abut to the end surface (61a; 61d) of the axial direction of an intermediate body for use.

According to a third aspect of the present invention, in the masking step, each of the masking members is elastically pressed into a corresponding tooth space by the spring property of the connecting member while being supported in a cantilevered manner by the connecting member. May be.
According to a fourth aspect of the present invention, in the masking step, each of the masking members may be held in a corresponding tooth space by a magnetic attractive force.

  According to the first aspect of the present invention, in the film forming step, the manufacturing intermediate can be accurately aligned with the broach using the circumferentially-equal metal exposed portion formed in the resin coating step. For this reason, a uniform resin film can be formed in a film formation process. Therefore, smooth sliding can be ensured for a long time on the spline telescopic shaft. In addition, since the resin coating disposed at the same axial position as the axial position where the metal exposed portion is disposed can also be used as a sliding region, the number of meshing teeth is increased, and the wear resistance of the resin coating is improved. A sufficient expansion / contraction stroke can be ensured.

In the invention of claim 2, a plurality of masking members can be collectively attached to the production intermediate, and workability is good. Moreover, the masking member can be accurately positioned in the axial direction of the manufacturing intermediate body by the contact of the connecting member with the axial end surface of the manufacturing intermediate body. For this reason, the axial position of the metal exposed portion can be set with high accuracy.
In invention of Claim 3, a masking member can be hold | maintained in a tooth gap using the spring property of a connection member.

  In the invention of claim 4, each masking member can be easily attached to and detached from the tooth gap and held.

It is a schematic diagram of the schematic structure of the steering device in which the spline telescopic shaft manufactured by the manufacturing method of the first embodiment of the present invention is applied to the intermediate shaft. It is a partially broken front view of the intermediate shaft concerning a 1st embodiment. It is an enlarged view of the III-III cross section of FIG. 4A is a side view of the inner shaft according to the first embodiment, FIG. 4B is a bb cross-sectional view of FIG. 4A, and FIG. It is cc sectional drawing of 4 (a). FIG. 5A to FIG. 5G are schematic views showing the manufacturing process of the inner shaft in the first embodiment. FIG. 6A is a schematic side view of the main part of the metal core member on which the masking member is mounted in the first embodiment, and FIG. 6B is a cross-sectional view taken along line bb in FIG. 6A. FIG. 6C is a side view of the unit including the masking member. It is an enlarged view of an axis perpendicular section of an important section of an intermediate shaft as a spline telescopic shaft manufactured by a manufacturing method of a 2nd embodiment of the present invention. 8A is a side view of the outer shaft according to the second embodiment, FIG. 8B is a cross-sectional view taken along line bb in FIG. 8A, and FIG. It is cc sectional drawing of 8 (a). FIGS. 9A to 9G are schematic views showing the manufacturing process of the outer shaft in the second embodiment. FIG. 10A is a schematic side view of a main part of a metal cylinder member to which a masking member is attached in the second embodiment, and FIG. 10B is a cross-sectional view taken along line bb in FIG. FIG. 10C is a side view of the unit including the masking member. FIGS. 11A and 11B are schematic cross-sectional views of the metal core material in the masking process according to the third and fourth embodiments of the present invention, respectively. FIG. 12A is a schematic side view of the metal core material in the masking step according to the fifth embodiment of the present invention. FIG.12 (b) is a schematic side view of the intermediate for manufacture obtained through the resin coating process. Fig.13 (a) is a schematic side view of the metal core material in the masking process which concerns on 6th Embodiment of this invention. FIG. 13B is a perspective view of a unit including a masking member used in the masking process. 14 (f1) and (g1) are schematic views showing a resin film forming process of the seventh embodiment as a modification of the resin film forming process of FIGS. 9 (f) and (g) of the second embodiment. .

A preferred embodiment of the present invention will be described with reference to the accompanying drawings.
(First embodiment)
FIG. 1 is a schematic view of a steering device 1 in which a spline telescopic shaft manufactured by the manufacturing method according to the first embodiment of the present invention is applied to an intermediate shaft (intermediate shaft) 5.

As shown in FIG. 1, the steering apparatus 1 includes a steering shaft (steering shaft) 3 having a steering wheel 2 connected to one end, and a steering column 20 disposed around the steering shaft 3.
The steering device 1 includes an intermediate shaft 5 as a spline telescopic shaft connected to the steering shaft 3 via a universal joint 4, a pinion shaft 7 connected to the intermediate shaft 5 via a universal joint 6, and a pinion shaft. And a rack shaft 8 as a steered shaft having a rack 8a meshing with the seven pinions 7a.

  The rack and pinion mechanism including the pinion shaft 7 and the rack shaft 8 constitutes the steering gear mechanism A1. The rack shaft 8 is supported by a housing 10 fixed to the vehicle body side member 9 so as to be movable in an axial direction along the left-right direction of the vehicle (a direction orthogonal to the paper surface). Although not shown, each end of the rack shaft 8 is connected to a corresponding steered wheel via a corresponding tie rod and a corresponding knuckle arm.

  The steering shaft 3 includes a first steering shaft 11 and a second steering shaft 12 that are connected coaxially. The first steering shaft 11 has an upper shaft 13 and a lower shaft 14 that are fitted so as to be capable of transmitting torque and sliding relative to each other in the axial direction using spline coupling. One of the upper shaft 13 and the lower shaft 14 constitutes an inner shaft, and the other constitutes a cylindrical outer shaft.

The second steering shaft 12 includes an input shaft 15 that is rotatably coupled to the lower shaft 14, an output shaft 16 that is connected to the intermediate shaft 5 via the universal joint 4, and the input shaft 15 and the output shaft. And a torsion bar 17 for connecting the 16 to each other so as to be relatively rotatable.
The steering column 20 is fixed to the vehicle body side members 18 and 19. The steering column 20 rotatably supports the steering shaft 3 via a bearing (not shown).

The steering column 20 includes a cylindrical upper jacket 21 and a cylindrical lower jacket 22 that are fitted so as to be relatively movable in the axial direction, and a housing 23 connected to the lower end in the axial direction of the lower jacket 22. The housing 23 houses a speed reduction mechanism 25 that decelerates the power of the steering assisting electric motor 24 and transmits it to the output shaft 16.
The speed reduction mechanism 25 includes a drive gear 26 that is coupled to a rotation shaft (not shown) of the electric motor 24 so as to be able to rotate together with the drive gear 26 and a driven gear 27 that meshes with the drive gear 26 and rotates together with the output shaft 16. . The drive gear 26 is composed of, for example, a worm shaft, and the driven gear 27 is composed of, for example, a worm wheel.

  The steering column 20 is fixed to the vehicle body side members 18 and 19 via an upper bracket 28 on the vehicle rear side and a lower bracket 29 on the vehicle front side. The upper bracket 28 can be fixed to the upper jacket 21 of the steering column 20 via a column bracket described later. The upper bracket 28 uses a fixing bolt (stud bolt) 30 that protrudes downward from the vehicle body side member 18, a nut 31 that is screwed to the fixing bolt 30, and a capsule 32 that is detachably held by the upper bracket 28. The vehicle body side member 18 is fixed.

The lower bracket 29 is fixed to the lower jacket 22 of the steering column 20. Further, the lower bracket 29 is fixed to the vehicle body side member 19 using a fixing bolt (stud bolt) 33 protruding from the vehicle body side member 19 and a nut 34 screwed into the fixing bolt 33.
The intermediate shaft 5 as a spline telescopic shaft includes an inner shaft 40 and an outer shaft 50 that is spline-fitted with the inner shaft 40. The inner shaft 40 and the outer shaft 50 can transmit torque to each other and can slide relative to each other in the axial direction X1. The outer shaft 50 is connected to the steering shaft 3 (specifically, the output shaft 16 of the second steering shaft 12) via the universal joint 4. The inner shaft 40 is connected to the pinion shaft 7 via the universal joint 6.

In the present embodiment, the outer shaft 50 constitutes an upper shaft, and the inner shaft 40 constitutes a lower shaft. However, the inner shaft 40 may constitute an upper shaft, and the outer shaft 50 may constitute a lower shaft.
In the present embodiment, the spline telescopic shaft manufactured by the manufacturing method of the present invention will be described as applied to the intermediate shaft 5, but the spline telescopic shaft is applied to the first steering shaft 11, The first steering shaft 11 may perform a telescopic adjustment function or an impact absorption function. The spline telescopic shaft may be applied to a manually steered steering device that does not use a steering assist force.

2 is a partially broken front view of the intermediate shaft 5, and FIG. 3 is a sectional view taken along the line III-III of FIG.
4A is a side view of the inner shaft according to the first embodiment, FIG. 4B is a cross-sectional view taken along line bb of FIG. 4A, and FIG. 4C is FIG. It is cc sectional drawing of).
As shown in FIGS. 2 and 4A, the inner shaft 40 has a spline shaft portion 41 in a range of a predetermined length from one end 40a in the axial direction X1. As shown in FIG. 2, the outer shaft 50 has a spline hole portion 51 that is spline-fitted with the spline shaft portion 41.

As shown in FIG. 2, the surface of the spline shaft portion 41 is disposed around the central axis C <b> 1 of the inner shaft 40. On the surface of the spline shaft portion 41, a male spline 42 as an external tooth portion is formed extending straight in the axial direction X1.
As shown in FIG. 4B, the inner shaft 40 includes a metal core material 60. The metal core member 60 has a metal spline shaft portion 61 that is a core material of the spline shaft portion 41, and a male spline 62 as a metal external tooth portion is formed on the surface of the spline shaft portion 61. Yes.

As shown in FIGS. 4B and 4C, the surface of the spline shaft portion 41 is a resin film except for a metal exposed portion 44 as a partial region where the surface of the metal core member 60 is exposed. 43 is formed.
That is, as shown in FIG. 4A, in the axial region L1 in the range of a predetermined length (at least 10 mm or more) in the axial direction X1 from the end portion 41a in the axial direction X1 of the spline shaft portion 41, FIG. ), The metal exposure is performed on the inner surface of a plurality of (two in the present embodiment) tooth grooves G arranged at equal circumferences of all the tooth grooves arranged in the circumferential direction Y1. A portion 44 (corresponding to the tooth surface of the male spline 62 of the metal core member 60) is disposed. In other words, the metal exposed portions 44 are arranged at two circumferentially equidistant locations in the circumferential direction Y1 of the spline shaft portion 41.

  The outer shaft 50 is made of metal, and as shown in FIGS. 2 and 3, the inner surface of the spline hole 51 of the outer shaft 50 is disposed around the central axis C <b> 2 (see FIG. 2) of the outer shaft 50. On the inner surface of the spline hole 51, a female spline 52 as an inner tooth portion is formed extending straight in the axial direction. As shown in FIG. 3, the tooth surface 42 t formed by the resin film 43 of the male spline 42 of the inner shaft 40 is engaged with the metal tooth surface 52 t of the female spline 52 of the outer shaft 50.

In FIG. 4A, the axial direction region L <b> 1 where the metal exposed portion 44 of the spline shaft portion 41 is provided is also used as a sliding region with respect to the outer shaft 50. That is, the resin coating [resin coating 43 in FIG. 4C] in the axial region L1 and the female spline 52 of the outer shaft 50 slide relative to each other in the axial direction X1.
5A to 5G show a process for manufacturing the inner shaft 40.

First, in the forging step [FIG. 5A], the metal core 60 having the spline shaft portion 61 having the male splines 62 as shown in FIG. 5B is obtained by forging the material.
Next, as shown in FIG. 5C, a masking member 70 is attached to the metal core member 60. Specifically, as shown in FIG. 6A, which is a schematic side view of the metal core member 60, masking members are respectively formed in the two tooth spaces G facing the radial direction of the male spline 62 of the metal core member 60. 70 is attached.

As shown in FIG. 6B, which is a bb cross-sectional view of FIG. 6A, each masking member 70 has a circular cross section. However, the cross section of the masking member 70 may be a bar having a trapezoidal shape or other polygonal shapes.
One end 70 a of each masking member 70 is connected to each other by a linear connecting member 71. As a result, an integral unit U including a plurality of masking members 70 and connecting members 71 is formed. For this reason, the masking member 70 can be collectively attached to the metal core member 60, and workability is good. The connecting member 71 may not be provided.

FIG. 6C is a side view of the unit U in a free state. As shown in FIG. 6C, the connecting member 71 supports one end 70a of both masking members 70 in a cantilevered manner. In the unit U in the free state, the distance between the other ends 70 b of both masking members 70 is smaller than the distance between the one ends 70 a of both masking members 70.
Accordingly, as shown in FIG. 6A, when the connecting member 71 is attached to the metal core member 60 with the distance between the other ends 70 b of both masking members 70 widened, With one end 70a as a fulcrum, the other end 70b is elastically rotated and biased so as to be close to each other. That is, each masking member 70 is elastically pressed to the corresponding tooth gap G by the spring property of the connecting member 71 while being supported in a cantilevered manner by the connecting member 71. For this reason, the holding force with respect to the corresponding tooth gap G of each masking member 70 can be increased.

Further, the connecting member 71 is in contact with the end surface 61a in the axial direction X1 of the spline shaft portion 61 of the metal core member 60 (corresponding to the end surface in the axial direction X1 of the metal core member 60), and is positioned in the axial direction X1. . For this reason, each masking member 70 is accurately positioned in the axial direction X1.
Next, a resin coating step [see FIG. 5 (d)] is performed. In the resin coating step, for example, a fluid dipping method is used. That is, after the pretreatment (for example, primer treatment) is performed on the metal core material 60 on which the masking member 70 is mounted, the metal core material 60 is heated, and the heated metal core material 60 is in a state where the resin powder is in a fluid state. It is immersed for a predetermined time in the fluidized immersion bath.

As a result, the resin powder adheres to the metal core member 60 and is melted by heat, whereby the surface of the male spline 42A has a spline shaft portion 41A formed with the resin layer 43A as shown in FIG. 6 (e). A production intermediate 40A is obtained.
That is, the surface of the male spline 62 of the metal core member 60 is covered with the resin layer 43A to obtain the male spline 42A, and the inner surfaces of some of the tooth grooves G covered with the respective masking members 70 in the male spline 42A are It is left as a plurality of exposed metal parts 44 arranged at equal circumferences.

Next, as shown in FIGS. 5F and 5G, a resin film forming step is performed. In the resin film forming step, the manufacturing intermediate 40 </ b> A on which the resin layer 43 </ b> A is formed is aligned with an annular surface broach 80 (also referred to as a die) through the plurality of exposed metal parts 44.
Specifically, as shown in FIG. 5 (f), a centering member 90 such as a ball plunger that elastically pushes the metal exposed portions 44 arranged at equal circumferences inward in the radial direction of the manufacturing intermediate 40A. Thus, the center axis C1 of the manufacturing intermediate 40A is aligned with the center axis C3 of the surface broach 80.

  More specifically, a circular hole 45 centering on the central axis C <b> 1 is formed on the end surface of the manufacturing intermediate body 40 </ b> A (the end surface of the metal core material on which the resin layer is not formed). The conical convex part 101 of the holding jig 100 is inserted. Thereby, the holding jig 100 and the centering member 90 jointly align the center axis C1 of the manufacturing intermediate 40A and the center axis C3 of the surface broach 80. However, this centering method is an example, and the present invention is not limited to this method.

The manufacturing intermediate 40A and the surface broach 80 in the state of being aligned in this way are relatively slid in the axial direction X1. Specifically, as shown in FIG. 5G, the holding jig 100 is pressed to the surface broach 80 side by a pressure member (not shown), whereby the manufacturing intermediate 40 </ b> A is processed into the processing hole 81 of the surface broach 80. Press fit inside.
When the manufacturing intermediate body 40A is press-fitted, the centering member 90 elastically retracts radially outward of the manufacturing intermediate body 40A when riding on the resin layer 43A, or immediately after passing through the metal exposed portion 44. Further, it may be retracted to a position where it does not interfere with the resin layer 43A. Even in such a case, the accuracy of the film thickness of the formed resin film can be increased. The reason is that the accuracy of the film thickness of the resin film to be formed is almost determined by the centering at the beginning of the press-fitting of the intermediate 40A for manufacturing (beginning of the bite). This is because the centering member 90 that abuts against the exposed metal exposed portion 44 prevents the manufacturing intermediate body 40A from falling.

Along with the press-fitting of the manufacturing intermediate 40A, the surplus portion 43AK of the resin layer 43A is scraped, and the inner shaft 40 having the resin film 43 [see FIG. 4A] having a uniform film thickness is obtained.
Next, although not shown, the inner shaft 40 is then taken out from the surface broach 80 and grease is applied to the surface of the resin film 43 of the inner shaft 40. The inner shaft 40 coated with grease is incorporated into the outer shaft 50, and the intermediate shaft 5 as a spline telescopic shaft is completed.

  In the manufacturing method of the present embodiment, in the resin film forming step, the manufacturing intermediate 40A is accurately aligned with the surface broach 80 using the circumferentially evenly exposed metal exposed portions 44 formed in the resin coating step. can do. For this reason, the uniform resin film 43 can be formed in the resin film forming step. Therefore, smooth sliding can be ensured for a long period of time on the intermediate shaft 5 which is a spline telescopic shaft.

Further, since the resin coating 43 [resin coating 43 in FIG. 4C] disposed at the same axial position as the axial position where the metal exposed portion 44 is disposed can also be used as a sliding region, Sufficient expansion / contraction stroke can be secured. Moreover, since the fitting area as the whole fitting part of the intermediate shaft 5 is ensured, the contact surface pressure of a fitting part can be reduced and durability can be improved.
(Second Embodiment)
FIG. 7 is an enlarged view of a cross section perpendicular to the axis of the main part of the intermediate shaft 5P as a spline telescopic shaft manufactured by the manufacturing method of the second embodiment of the present invention. 8A is a side view of the outer shaft according to the second embodiment, FIG. 8B is a cross-sectional view taken along line bb in FIG. 8A, and FIG. It is cc sectional drawing of 8 (a).

As shown in FIG. 7, the intermediate shaft 5P as a spline telescopic shaft includes an inner shaft 40P and an outer shaft 50P that is spline-fitted with the inner shaft 40P. The inner shaft 40P and the outer shaft 50P can transmit torque to each other and can slide relative to each other in the axial direction (a direction orthogonal to the paper surface in FIG. 7).
The inner shaft 40P is made of metal. On the outer surface of the spline shaft portion 41P of the inner shaft 40P, a male spline 42P as an external tooth portion is formed extending straight in the axial direction.

The outer shaft 50P has a spline hole 51P that is spline-fitted with the spline shaft portion 41P of the inner shaft 40P. A male spline 42P as an external tooth portion on the surface of the spline shaft portion 41P and a female spline 52P as an internal tooth portion on the inner surface of the spline hole portion 51P are fitted.
A tooth surface 53Pt formed by the resin coating 53P of the female spline 52P of the outer shaft 50P is engaged with the metal tooth surface 42Pt of the male spline 42P of the inner shaft 40P.

As shown in FIG. 8B, the outer shaft 50P includes a metal cylinder 60P. The metal cylinder 60P has a spline hole 61P penetrating in the axial direction, and a metal female spline 62P is formed on the inner surface of the spline hole 61P.
As shown in FIG. 8B and FIG. 8C, the surface of the spline hole 51P has a resin coating except for a metal exposed portion 54P as a partial region where the inner surface of the metal cylinder 60P is exposed. 53P is formed.

  That is, as shown in FIG. 8A, in the axial region L2 in the range of a predetermined length (at least 10 mm or more) in the axial direction X1 from the end portion 51Pa in the axial direction X1 of the spline hole 51P, FIG. ), The metal exposure is performed on the inner surface of a plurality of (two in the present embodiment) tooth grooves G arranged at equal circumferences of all the tooth grooves arranged in the circumferential direction Y1. The portion 54P (corresponding to the tooth surface of the female spline 62P of the metal cylinder 60P) is disposed. In other words, the metal exposed portions 54P are arranged at two locations that are equally spaced in the circumferential direction Y1 of the spline hole portion 51P.

In FIG. 8A, the axial direction region L2 in which the metal exposed portion 54P of the spline hole 51P is provided is also used as a sliding region with respect to the inner shaft 40P. That is, the resin coating [resin coating 53P in FIG. 8C] in the axial region L2 and the male spline 42P of the inner shaft 40P slide relative to each other in the axial direction X1.
9A to 9G show a process for manufacturing the outer shaft 50P.

First, in the forging step [FIG. 9A], a metal cylinder 60P having a spline hole 61P having a female spline 62P is obtained as shown in FIG. 9B by forging the material.
Next, as shown in FIG. 9C, a masking member 70P is attached to the metal cylinder 60P. Specifically, as shown in FIGS. 10 (a) and 10 (b), which are schematic cross-sectional views of the metal cylinder member 60P, two tooth spaces facing the radial direction of the female spline 62P of the metal cylinder member 60P. A masking member 70P is inserted and attached to C in the axial direction. One end 70Pa of both masking members 70P is connected by a linear connecting member 71P to form an integral unit UP.

FIG. 10C is a side view of the unit U in a free state. As shown in FIG. 10C, the connecting member 71P supports one end 70Pa of both masking members 70P in a cantilever manner. In the unit U in the free state, the distance between the other ends 70Pb of both masking members 70P is larger than the distance between the one ends 70Pa of both masking members 70P.
Therefore, as shown in FIG. 10 (a), when the masking member 70P is attached to the metal cylinder 60P with the distance between the other ends 70Pb of the masking members 70P reduced, the connecting member 71P With one end 70Pa as a fulcrum, the other end 70Pb has a spring property that elastically rotates and biases them away from each other. That is, each masking member 70P is elastically pressed into the corresponding tooth gap G by the spring property of the connecting member 71P while being supported in a cantilevered manner by the connecting member 71P. For this reason, the holding force with respect to the corresponding tooth gap G of each masking member 70P can be increased.

Further, the connecting member 71P is brought into contact with the end face 61Pa in the axial direction X1 of the spline hole 61P of the metal cylinder 60P (corresponding to the end face in the axial direction X1 of the metal cylinder 60P), and is positioned in the axial direction X1. . For this reason, each masking member 70P is accurately positioned in the axial direction X1.
Next, a resin coating step [see FIG. 9 (d)] is performed. In the resin coating step, for example, a fluid dipping method is used. That is, after the pretreatment (for example, primer treatment) is performed on the metal cylinder 60P on which the masking member 70P is mounted, the metal cylinder 60P is heated, and the heated metal cylinder 60P causes the resin powder to flow. It is immersed for a predetermined time in the fluidized immersion bath.

As a result, the resin powder adheres to the metal cylinder 60P and is melted by heat, so that the surface of the female spline 52PA has a spline hole 51PA formed of the resin layer 53PA as shown in FIG. 9 (e). Intermediate 50PA for production is obtained.
That is, the surface of the female spline 62P of the metal cylinder 60P is covered with the resin layer 53PA to obtain a female spline 52PA, and the inner surfaces of some of the tooth grooves G covered with the respective masking members 70P in the female spline 52PA It is left as a plurality of metal exposed portions 54P arranged at equal circumferences.

Next, as shown in FIGS. 9F and 9G, a resin film forming step is performed. In the resin film forming step, the manufacturing intermediate 50PA on which the resin layer 53PA is formed is aligned with the annular inner surface broach 80P through the plurality of exposed metal parts 54P.
Specifically, as shown in FIG. 9F, a centering member 90P supported by a holding jig 110 so as to be movable in the axial direction X1 and elastically biased in the axial direction X1 by a biasing member 91P, and a metal A centering member 90 (corresponding to the centering member 90 in the first embodiment of FIG. 5 (f)) that engages the tip of the inner surface broach 80P having a surface is used.

The centering member 90P is engaged with the exposed metal portion 54P arranged on the circumference of the intermediate body 50PA for manufacturing, and the centering member 90 passes the plurality of tooth grooves in the distal end portion of the inner surface broach 80P in the radial direction. By pressing elastically toward the center, the center axis C2 of the manufacturing intermediate 50PA is aligned with the center axis C4 of the inner surface broach 80P.
More specifically, a circular hole 82P centering on the central axis C4 is formed in the end face of the inner surface broach 80P having the machining axis 81P, and the conical convex portion 101 of the holding jig 100 is inserted into the circular hole. Is done. Thereby, the holding jig 100, the centering member 90, and the centering member 90P jointly align the center axis C2 of the manufacturing intermediate 50PA and the center axis C4 of the inner surface broach 80P. However, this centering method is an example, and the present invention is not limited to this method.

  The manufacturing intermediate 50PA and the inner surface broach 80P in the state of being aligned in this way are relatively slid in the axial direction X1. Specifically, as shown in FIG. 9 (g), the holding jig 100 is pressed by a pressing member (not shown) to the manufacturing intermediate 50PA side, whereby the inner surface broach 80P is splined to the manufacturing intermediate 50PA. Press fit into the hole 51PA. When the inner surface broach 80P is press-fitted, the centering member 90P abuts against the end surface of the machining shaft 81P of the inner surface broach 80P, thereby elastically retracting outward in the axial direction of the manufacturing intermediate 50PA.

Along with the press-fitting of the inner surface broach 80P, the surplus portion of the resin layer 53PA is scraped, and an outer shaft 50P having a uniform resin film 53P [see FIG. 8A] is obtained.
Then, although not shown, grease is then applied to the surface of the resin coating 53P of the outer shaft 50P removed from the inner surface broach 80P. The outer shaft 50P coated with grease is fitted with the inner shaft 40P, and the intermediate shaft 5P as a spline telescopic shaft is completed.

  In the manufacturing method of the present embodiment, in the resin film forming process, the manufacturing intermediate 50PA is accurately aligned with the inner surface broach 80P using the circumferentially-equal metal exposed portion 54P formed in the resin coating process. can do. For this reason, the uniform resin film 53P can be formed in the resin film forming step. Therefore, smooth sliding can be ensured for a long time on the intermediate shaft 5P which is a spline telescopic shaft.

Further, since the resin coating 53P [resin coating 53P in FIG. 8 (c)] disposed at the same axial position as the axial position where the metal exposed portion 54P is disposed can also be used as a sliding region, as the intermediate shaft 5P, Sufficient expansion / contraction stroke can be secured. Moreover, since the fitting area as the whole fitting part of intermediate shaft 5P is ensured, the contact surface pressure of a fitting part can be reduced and durability can be improved.
(Third and fourth embodiments)
FIGS. 11A and 11B are cross-sectional views of masking members used in the masking process of the third embodiment and the fourth embodiment, respectively.

The masking member 70Q of FIG. 11A is a shaft body including, for example, a rod-like permanent magnet 72 and a cover member 73Q in which the permanent magnet 72 is embedded in the center. The masking member 70Q has a circular cross section.
The masking member 70R in FIG. 11B is a shaft body including a permanent magnet 72 and a cover member 73R in which the permanent magnet 72 is embedded in the center, and is formed in a trapezoidal cross section. The slopes of the pair of trapezoidal leg portions 70Ra and 70Rb of the masking member 70R coincide with the slopes of the pair of tooth surfaces that define the tooth gap G.

The cover member 73Q; 73R is made of a heat resistant and magnetic material. For example, heat-resistant rubber or heat-resistant resin containing carbon as a magnetic material is used.
In the third and fourth embodiments, in the masking step, each masking member 70Q; 70R can be easily attached to and detached from the tooth gap G and held by a magnetic attraction force.
Although not shown, a masking member including an electromagnet may be used to attach and detach the masking member by turning on and off the electromagnet. Furthermore, you may comprise a masking member only with a permanent magnet.
(Fifth embodiment)
FIG. 12A is a schematic cross-sectional view of the metal core material in the masking process according to the fifth embodiment of the present invention. As shown in FIG. 12 (a), in the masking step, the spline shaft portion 61 of the metal core member 60 is separated from the two axial portions X1 in the axial direction X1 (for example, the axial region at both ends) or the axial region in the vicinity of both ends. A masking member (for example, 70Q) may be attached.

In this case, through the resin coating step, as shown in FIG. 12B, it is possible to obtain the manufacturing intermediate 40A in which the metal exposed portions 44 are formed at two positions in the axial direction. Therefore, in the resin film forming process (not shown), centering can be performed via the metal exposed portion 44 at two positions in the axial direction, so that the centering accuracy is improved.
(Sixth embodiment)
FIG. 13A is a schematic cross-sectional view of the metal core material in the masking step according to the fifth embodiment of the present invention. As shown in FIG. 13A, in the masking step, the unit U including the masking member 70 </ b> S of the first embodiment of FIG. 6 is disposed at the tip portion 61 b in the axial direction X <b> 1 of the spline shaft portion 61 of the metal core member 60. Installed. The unit US including the masking member 70S is attached to the other base end portion 61c of the spline shaft portion 61 in the axial direction X1.

  As shown in FIG. 13B, the unit US is an integral unit including a plurality of masking members 70S and a C-shaped connecting member 71S that connects one end 70Sa of each masking member 70S. As shown in FIG. 13A, the connecting member 71S is brought into contact with the stepped end surface 61d of the base end portion 61c of the metal core member 60, whereby the masking member 70S is accurately moved in the axial direction X1. Positioned.

The C-shaped connecting member 71S can be elastically deformed so as to increase the distance between the pair of end portions 71Sa in the circumferential direction, as indicated by white arrows in FIG. For this reason, the masking member 70 </ b> S can be attached to the base end portion 61 c of the spline shaft portion 61 from the radial direction.
(Seventh embodiment)
14 (f1) and (g1) are schematic views showing a resin film forming process of the seventh embodiment as a modification of the resin film forming process of FIGS. 9 (f) and (g) of the second embodiment. .

14 (f1) and (g1) of the present embodiment are mainly different from the resin film forming step of FIGS. 9 (f) and (g) of the second embodiment as follows.
As shown in FIG. 14F1, the outer shaft manufacturing intermediate 50PA is arranged with the end portion where the exposed metal portion 54P is formed facing the inner surface broach 80P.
The center axis C4 of the inner surface broach 80P is moved relative to the center axis C3 of the manufacturing intermediate 50PA by a centering member 90 such as a ball plunger that pushes the outer periphery of the front end portion of the inner surface broach 80P radially inward of the inner surface broach 80P. Temporarily aligned.

  The leading end of the inner surface broach 80P thus centered is press-fitted into the inlet of the spline hole 61P of the manufacturing intermediate 50PA at the initial stage of press-fitting, and the metal exposed portion 54P disposed at the inlet is inserted. With the function, the inner surface broach 80P and the manufacturing intermediate 50PA are aligned with high accuracy. At this time, the centering member 90 may be separated from the inner surface broach 80P, or may be elastically displaced so as to follow the center alignment by the metal exposed portion 54P.

Then, as shown in FIG. 14 (g1), the inner surface broach 80P is press-fitted into the back side of the spline hole 61P of the manufacturing intermediate 50PA, thereby forming an accurate resin film in the spline hole 61P. Can do.
The present invention is not limited to each of the above-described embodiments. For example, although not shown, the masking members are arranged at 3 to 5 locations in the circumferential direction of the metal core member 60 or the metal cylinder member 60P. Also good. The cross section of the masking member may be polygonal.

  The position where the metal core member 60 and the metal cylinder member 60P are masked by the masking member may be a position other than the tip of the metal core member 60 and the metal cylinder member 60P. In addition, the present invention can be variously modified within the scope of the claims.

  DESCRIPTION OF SYMBOLS 1 ... Steering device, 3 ... Steering shaft, 5 ... Intermediate shaft (spline telescopic shaft) 11 ... First steering shaft, 40; 40P ... Inner shaft, 40A ... Production intermediate, 41 ... Spline shaft portion, 42 ... Male spline (External teeth), 43 ... resin coating, 44 ... exposed metal, 50; 50P ... outer shaft, 50PA ... intermediate for production, 51; 51P ... spline hole, 52; 52P ... female spline (internal tooth) 53P ... resin coating, 54P ... metal exposed part, 60 ... metal core, 61 ... spline shaft part, 61a; 61d ... end face, 62 ... male spline (external tooth part), 60P ... metal cylinder, 61P ... spline hole Part, 62P ... female spline (inner tooth part), 70; 70P; 70Q; 70R; 70S ... masking member, 70a; 70Pa; 70Sa ... one end, 70b; 70Pb ... other end, 71; 71P; 72 ... Permanent magnet, 73Q; 73R ... Cover member, 80 ... Surface broach (die), 81 ... Machining hole, 80P ... Internal broach, 81P ... Machining axis, 90; 90P ... Centering member, C1, C2, C3 ... Center axis , G ... tooth gap, L1; L2 ... axial region, U; UP; US ... unit, X1 ... axial direction, Y1 ... circumferential direction

Claims (4)

Circumferential circumference in a predetermined axial region of a manufacturing intermediate consisting of either a metal core having a metal outer tooth portion in a ring shape or a metal cylinder having a metal inner tooth portion in a ring shape A masking step of covering a part of the tooth spaces arranged at equal intervals by a plurality of masking members arranged at equal intervals around the circumference;
A plurality of metals in which a synthetic resin is supplied to the surface of the tooth portion to form a resin layer, and inner surfaces of some of the tooth grooves in the circumferential direction covered with the plurality of masking members are arranged in a circumferentially uniform manner Resin coating process to leave as an exposed part,
With the intermediate for manufacturing on which the resin layer is formed aligned with the broach via the plurality of exposed metal parts, the intermediate for manufacturing and the broach are relatively slid in the axial direction by press fitting. And a film forming step of forming a resin film by shaving the resin layer, thereby producing a spline telescopic shaft.   2. The method of manufacturing a spline telescopic shaft according to claim 1, wherein in the masking step, a connecting member that connects one end of the plurality of masking members is in contact with an end surface in an axial direction of the manufacturing intermediate.   3. The spline according to claim 2, wherein, in the masking step, each masking member is elastically pressed into a corresponding tooth space by a spring property of the connecting member while being supported in a cantilevered manner by the connecting member. Manufacturing method of telescopic shaft.   2. The method of manufacturing a spline telescopic shaft according to claim 1, wherein in the masking step, each of the masking members is held in a corresponding tooth space by a magnetic attractive force.

Images